The invention relates to internal combustion engines of the type which require a spark plug. Such a known internal combustion engine, which has a main combustion chamber for each cylinder and an ignition chamber communicating therewith, has the disadvantage that the firing charge located in the ignition chamber, which after ignition exits as a jet of flame into the main combustion chamber, is the most highly heated zone, and in the course of the further compression which it undergoes, it is heated still further, when the remainder of the charge is consumed in the main combustion chamber. In a known manner, the formation of NO.sub.x is particularly apparent in the charge components which are highly heated. The larger the charge quantity and the higher the temperature, the higher will be the emission of NO.sub.x in the consumed charge as a whole.